Syrian state media claim 123 people have been killed in fighting in the northern town of Khan al-Assad in Syria

The Syrian Observatory for Human Rights, an anti-Assad monitoring group, said that more than 150 soldiers were killed on Monday and Tuesday in and around the town, including 51 soldiers and officers who were executed.

Meanwhile, the United Nations and Syria said this afternoon that negotiations between the Syrian government and UN chemical weapons investigator Ake Sellstrom were "productive".

However, they did not say if Mr Sellstrom’s team would be allowed to probe allegations that such weapons had been used in the country's civil war.

Mr Sellstrom's full team has not been allowed into Syria. His mission this week was to prepare the ground for an investigation.

Mr Sellstrom met Foreign Minister Walid al-Moualem, and a joint UN-Syrian statement said "discussions were thorough and productive and led to an agreement on the way forward".

It did not say if the agreement included access for Sellstrom's team.

Syria has so far refused to let UN investigators go anywhere except Khan al-Assal in Aleppo province, where Syrian President Bashar al-Assad's government and its ally Russia say rebels used chemical weapons in March.

The United States said last month it had proof that the Syrian government had used chemical weapons against fighters trying to overthrow Mr Assad.

UN Secretary-General Ban Ki-moon has insisted that his team be permitted to visit at least one other location, the city of Homs, site of an alleged chemical attack by government forces in December 2012.

Both sides deny using chemical weapons in a war which the UN says has killed 100,000 people.